Monthly Archives: October 2015

Speculation on Bromide and Bladder Cancer Risk

As in past studies such as this the assumptions made in this work drive the conclusions. Whether the results correspond to reality is a matter of speculation.

Regli S, Chen J, Messner M, Elovitz MS, Letkiewicz F, Pegram R, Pepping TJ, Richardson S, Wright JM. Estimating Potential Increased Bladder Cancer Risk Due to Increased Bromide Concentrations in Sources of Disinfected Drinking Waters. Environ Sci Technol. 2015 Oct 21.

Public water systems are increasingly facing higher bromide levels in their source waters from anthropogenic contamination through coal-fired power plants, conventional oil and gas extraction, textile mills, and hydraulic fracturing. Climate change is likely to exacerbate this in coming years. We estimate bladder cancer risk from potential increased bromide levels in source waters of disinfecting public drinking water systems in the United States. Bladder cancer is the health endpoint used by the United States Environmental Protection Agency (EPA) in its benefits analysis for regulating disinfection byproducts in drinking water. We use estimated increases in the mass of the four regulated trihalomethanes (THM4) concentrations (due to increased bromide incorporation) as the surrogate disinfection byproduct (DBP) occurrence metric for informing potential bladder cancer risk. We estimate potential increased excess lifetime bladder cancer risk as a function of increased source water bromide levels. Results based on data from 201 drinking water treatment plants indicate that a bromide increase of 50 µg/L could result in a potential increase of between 10-3 to 10-4 excess lifetime bladder cancer risk in roughly 90% of these plants.

Bromine Impact on DBP Formation

Attempting to remove bromide from source waters may not prove to be the best approach for controlling halogenated DBP formation.

Tan J, Allard S, Gruchlik Y, McDonald S, Joll CA, Heitz A. Impact of bromide on halogen incorporation into organic moieties in chlorinated drinking water treatment and distribution systems. The Science of the Total Environment. 2015 Oct 17;541:1572-1580. doi: 10.1016/j.scitotenv.2015.10.043.

The impact of elevated bromide concentrations (399 to 750μg/L) on the formation of halogenated disinfection by-products (DBPs), namely trihalomethanes, haloacetic acids, haloacetonitriles, and adsorbable organic halogen (AOX), in two drinking water systems was investigated. Bromine was the main halogen incorporated into all of the DBP classes and into organic carbon, even though chlorine was present in large excess to maintain a disinfectant residual. Due to the higher reactivity of bromine compared to chlorine, brominated DBPs were rapidly formed, followed by a slower increase in chlorinated DBPs. Higher bromine substitution and incorporation factors for individual DBP classes were observed for the chlorinated water from the groundwater source (lower concentration of dissolved organic carbon (DOC)), which contained a higher concentration of bromide, than for the surface water source (higher DOC). The molar distribution of adsorbable organic bromine to chlorine (AOBr/AOCl) for AOX in the groundwater distribution system was 1.5:1 and almost 1:1 for the surface water system. The measured (regulated) DBPs only accounted for 16 to 33% of the total organic halogen, demonstrating that AOX measurements are essential to provide a full understanding of the formation of halogenated DBPs in drinking waters. In addition, the study demonstrated that a significant proportion (up to 94%) of the bromide in source waters can be converted AOBr. An evaluation of AOBr and AOCl through a second groundwater treatment plant that uses conventional treatment processes for DOC removal produced 70% of AOX as AOBr, with 69% of the initial source water bromide converted to AOBr. Exposure to organobromine compounds is suspected to result in greater adverse health consequences than their chlorinated analogues. Therefore, this study highlights the need for improved methods to selectively reduce the bromide content in source waters.

Interventions to Prevent Water-Related Diarrhoea

Clasen TF, Alexander KT, Sinclair D, Boisson S, Peletz R, Chang HH, Majorin F, Cairncross S. Interventions to improve water quality for preventing diarrhoea. The Cochrane Database of Systematic Reviews. 2015 Oct 20;10:CD004794.

BACKGROUND: Diarrhoea is a major cause of death and disease, especially among young children in low-income countries. In these settings, many infectious agents associated with diarrhoea are spread through water contaminated with faeces. In remote and low-income settings, source-based water quality improvement includes providing protected groundwater (springs, wells, and bore holes), or harvested rainwater as an alternative to surface sources (rivers and lakes). Point-of-use water quality improvement interventions include boiling, chlorination, flocculation, filtration, or solar disinfection, mainly conducted at home.

OBJECTIVES: To assess the effectiveness of interventions to improve water quality for preventing diarrhoea.

SEARCH METHODS: We searched the Cochrane Infectious Diseases Group Specialized Register (11 November 2014), CENTRAL (the Cochrane Library, 7 November 2014), MEDLINE (1966 to 10 November 2014), EMBASE (1974 to 10 November 2014), and LILACS (1982 to 7 November 2014). We also handsearched relevant conference proceedings, contacted researchers and organizations working in the field, and checked references from identified studies through 11 November 2014.

SELECTION CRITERIA: Randomized controlled trials (RCTs), quasi-RCTs, and controlled before-and-after studies (CBA) comparing interventions aimed at improving the microbiological quality of drinking water with no intervention in children and adults.

DATA COLLECTION AND ANALYSIS: Two review authors independently assessed trial quality and extracted data. We used meta-analyses to estimate pooled measures of effect, where appropriate, and investigated potential sources of heterogeneity using subgroup analyses. We assessed the quality of evidence using the GRADE approach.

MAIN RESULTS: Forty-five cluster-RCTs, two quasi-RCTs, and eight CBA studies, including over 84,000 participants, met the inclusion criteria. Most included studies were conducted in low- or middle-income countries (LMICs) (50 studies) with unimproved water sources (30 studies) and unimproved or unclear sanitation (34 studies). The primary outcome in most studies was self-reported diarrhoea, which is at high risk of bias due to the lack of blinding in over 80% of the included studies. Source-based water quality improvementsThere is currently insufficient evidence to know if source-based improvements such as protected wells, communal tap stands, or chlorination/filtration of community sources consistently reduce diarrhoea (one cluster-RCT, five CBA studies, very low quality evidence). We found no studies evaluating reliable piped-in water supplies delivered to households. Point-of-use water quality interventions. On average, distributing water disinfection products for use at the household level may reduce diarrhoea by around one quarter (Home chlorination products: RR 0.77, 95% CI 0.65 to 0.91; 14 trials, 30,746 participants, low quality evidence; flocculation and disinfection sachets: RR 0.69, 95% CI 0.58 to 0.82, four trials, 11,788 participants, moderate quality evidence). However, there was substantial heterogeneity in the size of the effect estimates between individual studies.Point-of-use filtration systems probably reduce diarrhoea by around a half (RR 0.48, 95% CI 0.38 to 0.59, 18 trials, 15,582 participants, moderate quality evidence). Important reductions in diarrhoea episodes were shown with ceramic filters, biosand systems and LifeStraw® filters; (Ceramic: RR 0.39, 95% CI 0.28 to 0.53; eight trials, 5763 participants, moderate quality evidence; Biosand: RR 0.47, 95% CI 0.39 to 0.57; four trials, 5504 participants, moderate quality evidence; LifeStraw®: RR 0.69, 95% CI 0.51 to 0.93; three trials, 3259 participants, low quality evidence). Plumbed in filters have only been evaluated in high-income settings (RR 0.81, 95% CI 0.71 to 0.94, three trials, 1056 participants, fixed effects model).In low-income settings, solar water disinfection (SODIS) by distribution of plastic bottles with instructions to leave filled bottles in direct sunlight for at least six hours before drinking probably reduces diarrhoea by around a third (RR 0.62, 95% CI 0.42 to 0.94; four trials, 3460 participants, moderate quality evidence).In subgroup analyses, larger effects were seen in trials with higher adherence, and trials that provided a safe storage container. In most cases, the reduction in diarrhoea shown in the studies was evident in settings with improved and unimproved water sources and sanitation.

AUTHORS’ CONCLUSIONS: Interventions that address the microbial contamination of water at the point-of-use may be important interim measures to improve drinking water quality until homes can be reached with safe, reliable, piped-in water connections. The average estimates of effect for each individual point-of-use intervention generally show important effects. Comparisons between these estimates do not provide evidence of superiority of one intervention over another, as such comparisons are confounded by the study setting, design, and population. Further studies assessing the effects of household connections and chlorination at the point of delivery will help improve our knowledge base. As evidence suggests effectiveness improves with adherence, studies assessing programmatic approaches to optimising coverage and long-term utilization of these interventions among vulnerable populations could also help strategies to improve health outcomes.

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Clay and Clay Minerals for Removing Fluoride from Water

Vinati A, Mahanty B, Behera S.K. Clay and clay minerals for fluoride removal from water: A state-of-the-art review. Applied Clay Science. Sep2015, Vol. 114, p340-348.

The presence of fluoride in water has become a matter of great concern around the world due to its chronic human carcinogenic behavior. Developing easily accessible and environmentally sustainable removal strategies is therefore a challenge for the scientists. Among the different treatment technologies, adsorption process for fluoride removal is considered cost-effective, flexible, and easy to design and operate. This review discusses the recent trends in scientific research and development on the exploitation of clay and clay minerals for fluoride removal from water, focusing on the effect of various factors on the adsorption, mechanism, isotherms and kinetics of the adsorption process.

 

Perchlorate Removed by a Micelle-Clay Complex

Nir S, Brook I, Anavi Y, Ryskin M, Ben- Ari J, Shveky- Huterer R, Etkin H, Zadaka-Amir D, Shuali U. Water purification from perchlorate by a micelle–clay complex: Laboratory and pilot experiments. Applied Clay Science. Sep2015, Vol. 114, p151-156.

A technology for purification of water from perchlorate by filters including a complex between micelles of octadecyltrimethylammonium (ODTMA) and a clay-mineral, montmorillonite (Mt), or bentonite is presented. Laboratory filters of lengths of 20 and 40 cm were filled with a powdered micelle (ODTMA)–Mt complex mixed with excess sand at ratios of 1:100 to 1:15 w/w. A pilot filter (60 cm diameter ∙ 110 cm length) was filled with a 1:19 mixture. The complex exhibited a relatively large affinity to adsorb perchlorate; the presence of other anions, such as chloride, nitrate and sulfate at concentrations exceeding 1000-fold those of perchlorate had little effect on its removal from water by filtration. This high affinity was explained by the fact that the positively charged complex has abundance of hydrophobic regions, whereas perchlorate, is characterized by a large bare anionic radius, i.e., a loose hydration shell. A model which accounts for convection, adsorption and desorption was adequate in simulating and predicting the kinetics of filtration for two orders of magnitude variation in concentrations of perchlorate and one order of magnitude variations in concentrations of adsorbing sites, filter length, and flow velocities. Production of a granulated complex enabled to fill the filters exclusively with the complex and make the technology suitable for upscale. Based on the results of pilot experiments and model calculations, it is suggested that in comparison with other technologies, the micelle–clay filter has a relatively large capacity to remove perchlorate in the range of hundreds to thousands μg/l.

A Hybrid NF/RO System for Nitrate Removal

A hybrid NF/RO filtration scheme for nitrate removal is proposed and tested. Production of low salinity brines allowed to be discharged to sewerage systems. The new scheme can be applied in single or double NF stage modes prior to RO step. Appropriate NF membranes for the process should reject Cl better than NO3. The results show the process to be both technically feasible and energy efficient.

Epsztein R, Nir O, Lahav O, Green M. Selective nitrate removal from groundwater using a hybrid nanofiltration–reverse osmosis filtration scheme. Chemical Engineering Journal 1 November 2015 279:372-378

A novel and potentially cost effective filtration scheme for removal of nitrate from groundwater, characterized by production of low salinity waste brine that can be easily discharged to sewerage systems and high product-water recovery, is proposed. The inherent preference of particular NF membranes for rejecting chloride and sodium over nitrate ions is utilized in a preliminary NF stage to remove Na+, Cl+, Ca2+ and Mg2+ to a side stream. In a second stage, RO is applied to remove NO3 and the RO permeate is mixed with the side stream of the NF stage to create product water low in nitrate, yet with a balanced composition consisting all the required species and minerals. The number of NF stages depends mainly on the rejection efficiency of the NF membrane. Based on Israeli regulations for both drinking water and required composition of brines discharged to the sewage, a treatment scheme composed of a single and double NF stages followed by RO is shown to reach water recoveries of 91.6% and 94.3%, respectively. Each NF stage raises the energy cost by approximately 0.5cent/m3 product water. However, this cost is easily paid back by the inherent additional advantages of the combined scheme, i.e., less water treated by the RO, significant increase in total recovery ratio, no need in re-mineralization of the product water and minimization of calcium carbonate precipitation potential on the RO membrane. The principles for process design are described, making the specific treatment scheme proposed here easily adjustable to other regulatory requirements and other water characteristics. A provisional patent has been filed.